Laser printers that reproduce digital medical images on film have found increasing usage in the health care industry. Conventional laser printers produce films which are chemically processed to develop the images on the film. Photothermographic printers have recently been introduced that employ heat instead of chemical processing to develop the images. A photothermographic laser printer exposes the photothermographic film to a laser beam raster scanned on the film to produce a latent image. The exposed photothermographic film is thermally processed to develop the latent image into a visible image.
Photothermographic or dry laser printers have the following advantages: 1) customer convenience and reduced operating costs by not having to buy or dispose of chemistry or repair wet processors; 2) reduction in site preparation costs by not having to install water pipes and drains; and 3) higher reliability of dry printers by eliminating wet processors.
In order to produce uniformly exposed and processed laser printed film, it is necessary to calibrate the printer/processor system. Calibration is a process by which the inherent non-linear curve (input digital image code value vs. film output density) of the laser scan engine, film, and processor is systematically standardized to a linear code value to output density response curve. In addition, calibration maintains this response over time by compensating for the variation to all sub-components of the system.
The following disclose imaging systems which use the output density of developed film to change the exposure of the film to calibrate the system. U.S. Pat. No. 4,278,347, issued Jul. 14, 1981, inventors Okamoto et al.; U.S. Pat. No. 4,757,334, issued Jul. 12, 1988, inventor Valent; PCT unexamined International Patent Application WO 95/30934, published Nov. 16, 1995, inventors Star et al. There is no disclosure in any of the above of changing processor parameters to establish and maintain calibration of the system.